Retainer for ball bearing, and ball bearing

ABSTRACT

A retainer for a ball bearing includes two annular members that face each other in an axial direction thereof. The two annular members include opposed surfaces each having hemispherical pockets that are formed at positions in a circumferential direction of each of the two annular members and configured to receive balls. The opposed surfaces are snap-fitted to each other to couple together the two annular members. The hemispherical pockets each have an inner peripheral surface provided with ball contact and ball non-contact surfaces. The ball contact surface is formed at a central portion in a pocket circumferential direction and at least at a central portion in a pocket axial direction of the inner peripheral surface. The ball non-contact surface includes a recess recessed to an opposite side to a corresponding ball across the ball contact surface and is opened in at least one of pocket axial ends.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.14/114,588, filed Oct. 29, 2013.

BACKGROUND OF INVENTION

1. Technical Field

The present invention relates to a synthetic resin retainer for a ballbearing, which is configured to retain balls in a freely rollablemanner, and to a ball bearing having the retainer interposed between anouter race and an inner race.

2. Background Art

Various sealed ball bearings, such as a deep groove ball bearing and anangular contact ball bearing, are widely used, for example, for a gearsupport shaft of a transmission of a vehicle including an engine.

A ball bearing of this type includes an inner race having a radiallyouter surface formed as an inner raceway surface, an outer race arrangedon an outer side with respect to the inner race and having a radiallyinner surface formed as an outer raceway surface, and a plurality ofballs interposed in a freely rollable manner between the inner racewaysurface of the inner race and the outer raceway surface of the outerrace. A retainer is arranged between the inner race and the outer raceso as to equiangularly retain the balls. Further, seal portions arearranged in an annular space formed between the inner race and the outerrace. Any one of the outer race and the inner race is mounted to a fixedpart such as a housing, and another is mounted to a rotary part such asa rotary shaft.

In particular, in electric vehicles and hybrid vehicles, high-speedmotor rotation is input, and hence the rotary part such as the rotaryshaft tends to perform high rotation. As a result, there arise problemssuch as deformations of a retainer due to a lack of lubrication, torque(heat generation), and to a centrifugal force. The deformations of theretainer due to the lack of lubrication and the torque (heat generation)can be solved by appropriately designing a shape of the retainer.Further, the deformation of the retainer due to the centrifugal forcecan be suppressed by using a lightweight synthetic resin retainer.Meanwhile, ball bearings for automotive auxiliary electrical components(such as a motor and an alternator) are used under a state of beingsealed from both sides, and hence a lubricant such as grease needs to beused.

There have been proposed various lightweight synthetic resin retainersfor the purpose of suppressing the deformation of the retainers due tothe centrifugal force (for example, refer to Patent Literature 1). Theretainer disclosed in Patent Literature 1 is what is called a resincrown-shaped retainer including an annular main part, and pairs ofelastic pieces equiangularly and integrally projected at intervals onone side in an axial direction of the main part. Then, pockets eachopened to a radially outer side and a radially inner side are formedrespectively between the pairs of elastic pieces, and balls are retainedin the pockets in a freely rollable manner.

Further, as a countermeasure against the torque (heat generation) and inorder to use the retainer irrespective of the axial orientation of thebearing, it is preferred that the retainer be formed into a symmetricalshape in the axial direction. Thus, it is essential to provide astructure for coupling separate retainers to each other. Under thecircumstance, there have conventionally been proposed various retainerstructures for coupling two annular members to each other (PatentLiteratures 2 to 6).

CITATION LIST

Patent Literature 1: JP 2007-32821 A

Patent Literature 2: JP 2006-226430 A

Patent Literature 3: JP 2006-226447 A

Patent Literature 4: JP 2006-226448 A

Patent Literature 5: JP 2008-64221 A

Patent Literature 6: JP 2009-281399 A

Technical Problems

By the way, in the crown-shaped retainer disclosed in Patent Literature1, as described above, the balls are retained only from one side. Thus,when a significant centrifugal force is applied, such a retainer may benon-uniformly deformed. As a result, the balls may drop off from thepockets, and may interfere with other components such as the inner raceand the outer race.

By the way, the retainer disclosed in Patent Literature 1 has astructure including recessed groove-like thinned portions provided alonga circumferential direction in aback surface opposite to an opposedsurface provided with the pockets. The thinned portions are provided,for example, to substantially equalize thicknesses of parts of theretainer so as to suppress a deformation due to non-uniformity inthickness, and to achieve light-weighting of the retainer.

However, in the structure including the thinned portions provided in theback surface of the retainer, during rotation of the retainer, alubricant filled inside the bearing enters the thinned portions in theback surface of the retainer. As a result, stirring resistance of thelubricant may be increased, and an imbalance force may be applied to theretainer. Thus, smooth rotation may be affected. In particular, at thetime of high-speed rotation, the stirring resistance of the lubricantincreases, and hence torque (heat) to be generated between the retainerand the balls is difficult reduce. This is a serious problem because, inrecent years, torque reduction of automotive ball bearings is demandedalso in view of environmental issues for higher fuel efficiency and thelike.

As described in Patent Literatures 2 to 6, in the retainers formed intoa symmetrical shape in the axial direction, the pockets for retainingsteel balls (balls) each have an inner peripheral surface formed of auniform curve surface in conformity with the balls. Thus, resistanceagainst shearing by the balls with respect to an oil (lubricant such asgrease) is generated. This shearing resistance is generated at the timeof shearing oil films formed between an internal side of the pocket andthe steel ball (ball) held in the pocket. Further, resistance isgenerated at the time of passage of the lubricant through a minute gapbetween the ball and the internal side of the pocket of the retainer forcovering the ball. In this way, in the conventional retainers, reductionin torque is difficult to achieve.

SUMMARY OF INVENTION

Under the circumstances, the present invention has been proposed in viewof the problems described above, and it is an object thereof to providea retainer for a ball bearing and a ball bearing, which are capable ofreducing torque.

Solution to Problems

According to one embodiment of the present invention, there is provideda resin retainer for a ball bearing, comprising a pair of annularmembers that face each other in an axial direction thereof, the pair ofannular members having opposed surfaces each comprising hemisphericalpockets that are formed at a plurality of positions in a circumferentialdirection of each of the pair of annular members and configured toreceive balls, the pair of annular members being integrated with eachother in a symmetrical shape in which the pair of annular membersoverlap each other in the circumferential direction, in which thehemispherical pockets each have an inner peripheral surface including aball contact surface and a ball non-contact surface, in which the ballcontact surface is formed at a central portion in a pocketcircumferential direction of the inner peripheral surface and at leastat a central portion in a pocket axial direction of the inner peripheralsurface, in which the ball non-contact surface comprises a recess thatis recessed to an opposite side to corresponding one of the balls acrossthe ball contact surface, and in which the recess is opened in at leastone of pocket axial ends.

According to the retainer for a ball bearing, the ball non-contactsurface is provided on the inner peripheral surface, and hence a reliefportion for a lubricant can be formed on an internal side of each of thehemispherical pockets. With this, not only resistance generated at thetime of passage of the lubricant through the internal side of each ofthe hemispherical pockets, but also an amount of oil films to be formedbetween the balls and the hemispherical pockets can be reduced. Inaddition, the recess forming the ball non-contact surface is opened inthe at least one of the pocket axial ends, and hence extra lubricantbetween the inner peripheral surface of the retainer for a ball bearingand the balls (steel balls) can be discharged therethrough. Further, theball contact surface is provided at the central portion of the innerperipheral surface, and hence each of the balls (steel balls) can bestably retained in the pocket central portion.

The ball contact surface may be formed at the central portion in thepocket axial direction and at the central portion in the pocketcircumferential direction of the inner peripheral surface of each of thehemispherical pockets, and the ball non-contact surface may comprise aC-shaped recess comprising: parts provided on both sides in the pocketcircumferential direction of the ball contact surface; and a partprovided on a side of one of the pocket axial ends on a bearing radiallyouter side. With this setting, the lubricant between the innerperipheral surface and each of the balls can be more easily dischargedby a centrifugal force.

The ball contact surface may comprise an oblong portion formed at thecentral portion in the pocket circumferential direction of the innerperipheral surface so as to reach both the pocket axial ends, the ballnon-contact surface may comprise circular-arc recesses provided on bothsides in the pocket circumferential direction of the ball contactsurface, and the circular-arc recesses may be each opened in both thepocket axial ends. Also with this setting, extra lubricant between theinner peripheral surface and each of the balls can be discharged from abearing radially outer side and a bearing radially inner side.

It is preferred that the retainer further comprise coupling portions forcoupling the two annular members to each other by snap-fitting theopposed surfaces to each other, that the coupling portions be providedat both end portions in the circumferential direction of the each of thehemispherical pockets, and that the two annular members each have a backsurface located on an opposite side to corresponding one of the opposedsurfaces and formed into a flat shape over an entire periphery thereof.

In this way, when the back surface located on the opposite side to eachof the opposed surfaces that are snap-fitted to each other for couplingthe two annular members to each other with the coupling portionsprovided at both the end portions in the circumferential direction ofeach of the hemispherical pockets is formed into a flat shape over theentire periphery thereof, thinned portions need not be provided unlikeconventional retainers. Thus, stirring resistance of the lubricant isnot increased during rotation. As a result, torque (heat) to begenerated between the retainer for a ball bearing and the balls can beeasily reduced.

It is desired that this retainer for a ball bearing have a structure inwhich the coupling portions each comprise: a radially outer projectionformed by extending, in the axial direction, a radially outer side ofthe end portion in the circumferential direction of the each of thehemispherical pockets of one of the two annular members so as to allowan inner peripheral surface thereof to abut against the correspondingone of the balls; a radially inner recess formed by recessing a radiallyinner side of the end portion in the circumferential direction; aradially inner projection formed by extending, in the axial direction, aradially inner side of the end portion in the circumferential directionof the each of the hemispherical pockets of another of the two annularmembers so as to allow an inner peripheral surface thereof to abutagainst the corresponding one of the balls; and a radially outer recessformed by recessing a radially outer side of the end portion in thecircumferential direction, in which the radially outer projection andthe radially inner projection are engaged with each other in the axialdirection by inserting the radially outer projection into the radiallyouter recess and by inserting the radially inner projection into theradially inner recess, and in which an engagement surface of theradially outer projection and an engagement surface of the radiallyinner projection are inclined with respect to the axial direction in amanner that the radially outer projection and the radially innerprojection are each thicker on a distal end side than on a proximal endside.

In this retainer for a ball bearing, when the radially outer projectionand the radially inner projection are engaged with each other in theaxial direction, a frictional force is generated along each of theengagement surface of the radially outer projection and the engagementsurface of the radially inner projection. Further, the engagementsurface of the radially outer projection and the engagement surface ofthe radially inner projection are inclined with respect to the axialdirection in a manner that the radially outer projection and theradially inner projection are each thicker on the distal end side thanon the proximal end side. As a result, an axial component of a reactiveforce generated in a normal direction of each of the engagement surfaceof the radially outer projection and the engagement surface of theradially inner projection is provided. The frictional force generatedalong each of the engagement surface of the radially outer projectionand the engagement surface of the radially inner projection, and theaxial component of the reactive force generated in the normal directionof each of the engagement surfaces are applied synergistically with eachother. Thus, even when a significant centrifugal force is applied due tohigh rotation, the two annular members can be reliably prevented frombeing separated from each other in the axial direction.

In this retainer for a ball bearing, it is desired that, in each of thecoupling portions, an inclination angle of the engagement surface of theradially outer projection and an inclination angle of the engagementsurface of the radially inner projection be each set to 5° or more. Whenthe inclination angles are set to this value, deformation of theengagement surfaces at the time of application of a significantcentrifugal force due to high rotation can be easily suppressed. As aresult, the axial component of the reactive force can be reliablyapplied to the engagement surfaces, and hence a force of coupling thetwo annular members to each other can be easily secured. Note that, whenthe inclination angle of each of the engagement surfaces is less than5°, in the case where a significant centrifugal force is applied due tohigh rotation, the deformation of the engagement surfaces is difficultto suppress. As a result, the axial component of the reactive force isdifficult to reliably apply to the engagement surfaces.

It is desired that this retainer for a ball bearing have a structure inwhich, in the each of the coupling portions, the radially innerprojection is formed to be thicker than the radially outer projection.With this, at the time of the application of a significant centrifugalforce due to high rotation, the radially inner projection is deformedmore significantly than the radially outer projection. This is becausethe radially inner projection is larger than the radially outerprojection not only in thickness but also in mass. Here, the engagementsurface of the radially outer projection and the engagement surface ofthe radially inner projection are inclined with respect to the axialdirection in a manner that the radially outer projection and theradially inner projection are each thicker on the distal end side thanon the proximal end side. Thus, the radially inner projection isdeformed to increase the force of coupling the engagement surface of theradially outer projection and the engagement surface of the radiallyinner projection to each other.

It is desired that this retainer for a ball bearing have a structure inwhich, in the each of the coupling portions, the radially outerprojection and the radially inner recess are formed at one of both theend portions in the circumferential direction of the each of thehemispherical pockets, and the radially inner projection and theradially outer recess are formed at another of both the end portions inthe circumferential direction of the each of the hemispherical pockets.With this structure, annular members of one type can be manufacturedwith the same die set and respectively used as one of the two annularmembers and another of the two annular members. Thus, manufacturing costcan be reduced.

The retainer may further comprise flange portions provided respectivelyto a radially outer portion on an opposite side to the each of thecoupling portions of the two annular members, and to a radially innerportion on the opposite side to the each of the coupling portions. Withsuch flange portions thus provided, it is possible to restrict inflow ofthe lubricant into an inside (inside of the bearing) and prevent outflowof the lubricant from the inside (inside of the bearing) to the outsideof the bearing.

In this retainer for a ball bearing, it is desired that the each of thehemispherical pockets have a circumferential clearance set to be largerthan an axial clearance thereof. With this, even under a high momentload, circumferential lead and lag of each of the balls in thehemispherical pockets can be absorbed. As a result, durability of theretainer for a ball bearing can be enhanced. In this case, it is desiredthat the circumferential clearance of the each of the hemisphericalpockets be set to be 1.38 times or more as large as the axial clearancethereof. With this, under a high moment load, the circumferential leadand lag of each of the balls in the hemispherical pockets can bereliably absorbed. Note that, in each of the hemispherical pockets, whenthe circumferential clearance is less than 1.38 times as large as theaxial clearance, the circumferential lead and lag of each of the ballsin the hemispherical pockets is difficult to reliably absorb.

By the way, in the present invention, it is preferred that the twoannular members be each made of a synthetic resin in view oflight-weighting of the retainer for a ball bearing. In particular, as amaterial for the retainer for a ball bearing, there may be used any oneof a polyamide resin, a polyether ether ketone resin (PEEK), and apolyphenylene sulfide resin (PPS). As the polyamide resin, there may beused a polyamide 66 (PA66), a polyamide 46 (PA46), a polyamide 9T(PA9T), a polyamide 11 (PA11), or a polyamide 6 (PA6). The polyamideresin such as PA66 is excellent in tensile elongation, tensile strength,shock resistance, abrasion resistance, lubricity, and the like. Thepolyphenylene sulfide resin (PPS) is engineering plastic excellent inheat resistance, chemical resistance, and forming precision. Thepolyether ether ketone resin (PEEK) is a thermoplastic resin havingmarkedly high heat resistance, and having not only excellent fatigueresistance but also excellent abrasion resistance, dimensionalstability, and chemical resistance.

A ball bearing may comprise: the retainer for a ball bearing, which isstructured as describe above, an outer race; an inner race; and ballsinterposed between the outer race and the inner race, the outer race andthe inner race being rotated relative to each other. In particular, thepresent invention is suited to a sealed ball bearing comprising a sealportion that is arranged in an annular space formed between the innerrace and the outer race, and comprises a seal lip formed of an elasticmember.

It is preferred that the ball bearing be applied to a transmission. Thetransmission refers to a main speed change device for converting a driveforce from an engine to speed and transmitting the drive force thusconverted to a drive shaft and the like, and is roughly classified intoa manual type and an automatic type. Further, depending on a drivesystem of a vehicle, the transmission also refers to a front-wheel drive(FWD) transaxle, a rear-wheel drive (RWD) transmission, and a four-wheeldrive (4WD) transfer (auxiliary speed change device). The ball bearingis interposed, for example, between a main shaft and a main drive gear.

Advantageous Effects of Invention

In the retainer for a ball bearing according to the present invention,it is possible to reduce the resistance generated at the time of passageof a lubricant through the inside of the pockets, and an amount of oilfilms to be sheared due to movement of the balls. As a result, reductionin torque of the bearing (ball bearing) using this retainer can beachieved. In addition, extra lubricant between the inner peripheralsurface and the balls (steel balls) can be discharged therethrough. As aresult, the effect of the extra lubricant on the torque can beeliminated. Further, each of the balls (steel balls) can be stablyretained in the pocket central portion. Thus, it is possible to preventbacklash of the balls, and provide a high-quality product. In addition,with use of the two annular members, deformation due to a centrifugalforce and drop-off of the ball can be effectively prevented.

Irrespective of whether the ball non-contact surface is provided on thepocket axial end side or on both sides in the pocket circumferentialdirection of the ball contact surface, extra lubricant between surfacesopposed to the balls and the balls can be discharged. In this way, theeffect of the extra oil on the torque can be stably eliminated.

With the flange portions provided as described above, it is possible torestrict the inflow of the lubricant into the inside (inside of thebearing) and prevent the outflow of the lubricant from the inside(inside of the bearing) to an outside of the bearing. Thus, thelubricant can be stably maintained, and effective reduction in torquecan be achieved.

When the back surface located on the opposite side to each of theopposed surfaces that are snap-fitted to each other for coupling the twoannular members to each other with the coupling portions provided atboth the end portions in the circumferential direction of each of thepockets is formed into a flat shape over the entire periphery thereof,thinned portions need not be provided unlike conventional retainers.Thus, stirring resistance of the lubricant is not increased duringrotation. As a result, torque (heat) to be generated between theretainer and the balls can be easily reduced.

As a material for the retainer, there may be used a polyamide resinexcellent in tensile elongation, tensile strength, shock resistance,abrasion resistance, lubricity, and the like. Accordingly, it ispossible to provide a high-quality retainer.

According to the ball bearing of the present invention, deformation ofthe retainer due to high-speed rotation can be suppressed, and reductionin torque can be achieved through the restriction on an amount of theinflow of a lubricant and the reduction of the stirring resistance.Thus, when this bearing is used in an automobile, fuel efficiencybecomes higher, and hence environmentally friendly driving can beperformed. In other words, an automotive ball bearing suited to highrotation bearings used in electric vehicles and hybrid vehicles can beprovided. In particular, this ball bearing is optimum to automotivetransmissions.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a sectional view of a ball bearing using a retainer accordingto an embodiment of the present invention.

FIG. 2 is an enlarged perspective view of a main part of the retainerillustrated in FIG. 1.

FIG. 3 is a perspective view illustrating a pre-assembly state of theretainer illustrated in FIG. 1.

FIG. 4 is a perspective view illustrating an assembled state of theretainer illustrated in FIG. 1.

FIG. 5 is a developed view illustrating the pre-assembly state of theretainer illustrated in FIG. 1.

FIG. 6 is a developed view illustrating the assembled state of theretainer illustrated in FIG. 1.

FIG. 7 is a sectional view taken along the line VII-VII in FIG. 5.

FIG. 8 is a sectional view taken along the line VIII-VIII in FIG. 5.

FIG. 9 is a sectional view taken along the line IX-IX in FIG. 6.

FIG. 10 is a sectional view taken along the line X-X in FIG. 6.

FIG. 11 is a sectional view of a ball bearing using a retainer accordingto another embodiment of the present invention.

FIG. 12 is an enlarged perspective view of a main part of the retainerillustrated in FIG. 11.

FIG. 13 is a sectional view of a ball bearing comprising seal portions.

DESCRIPTION OF EMBODIMENTS

In the following, description is made of embodiments of the presentinvention with reference to the drawings.

A ball bearing 1 according to this embodiment comprises, as a main part,an inner race 2 having a radially outer surface formed as an innerraceway surface 2 a, an outer race 3 arranged on an outer side withrespect to the inner race 2 and having a radially inner surface formedas an outer raceway surface 3 a, a plurality of balls 4 interposed in afreely rollable manner between the inner raceway surface 2 a of theinner race 2 and the outer raceway surface 3 a of the outer race 3, anda retainer 5 arranged between the inner race 2 and the outer race 3 soas to equiangularly retain the balls 4. Any one of the outer race 3 andthe inner race 2 is mounted to a fixed part such as a housing, andanother is mounted to a rotary part such as a rotary shaft.

As illustrated in FIG. 3, the retainer 5 comprises two annular members10 facing each other in an axial direction thereof and having opposedsurfaces 11 each comprising hemispherical pockets 12 that are formed ata plurality of positions in a circumferential direction of the annularmembers 10 and configured to receive the balls 4, and has a symmetricalshape in which the two annular members 10 are coupled to each other bysnap-fitting the respective opposed surfaces 11 of the annular members10 to each other. The retainer 5 according to this embodiment comprisesa coupling structure (described below) for coupling the two annularmembers 10 to each other.

As illustrated in FIG. 2, the pockets 12 of the retainer 5 each have aninner peripheral surface including a ball contact surface 30 and a ballnon-contact surface 31. In other words, the inner peripheral surface ofeach of the pockets 12 has a recess 32, and the recess 32 forms the ballnon-contact surface 31.

The recess 32 as the ball non-contact surface 31 is a C-shaped recesscomprising a pocket peripheral portion 32 a arranged on a side of one ofpocket axial end portions (radially outer side), and a pair of endportions 32 b and 32 b arranged on both end sides of the pocketperipheral portion 32 a and extending inward. Thus, the ball contactsurface 30 comprises an intermediate part 30 a arranged between the endportions 32 b and 32 b of the recess, a pocket peripheral portion 30 bon a radially inner side, and end portions 30 c and 30 c on the radiallyouter side.

The recess 32 as the ball non-contact surface 31 is opened (released) inone of pocket axial ends (retainer radially outer surface 10 a). Therecesses 32 and 32 of the annular members 10 and 10 are arranged on thesame side in a pocket axial direction (on bearing radially outer side)so as to face each other when the pair of the annular members 10 and 10are assembled with each other (refer to FIG. 1).

A radially outer portion and radially inner portion on an opposite sideto coupling portions of each of the annular members 10 respectivelycomprise flange portions 24 a and 24 b. In other words, the flangeportion 24 a on the bearing radially outer side extends to the bearingradially outer side, and the flange portion 24 b on a bearing radiallyinner side extends to the bearing radially inner side. In this case, endsurfaces 21 on the opposite side to the coupling portions are eachformed into a flat shape (flat surface) parallel to a bearing axial endsurface, and end surfaces of the flange portions 24 a and 24 b on theopposite side to the coupling portions are inclined to project towardthe coupling portions side. Note that, in conformity with the flangeportions 24 a and 24 b thus provided, peripheral cutout portions 22 areprovided along axial end portions of the radially inner surface of theouter race 3, and peripheral cutout portions 23 are provided along axialend portions of the radially outer surface of the inner race 2.

As means for coupling the two annular members 10 to each other, theretainer 5 described above in this embodiment comprises the couplingstructure described below. Note that, in FIGS. 3 to 6 for describing thecoupling structure, the flange portions 24 a and 24 b are omitted forthe sake of simplicity of illustration. Thus, the retainer 5 illustratedin FIGS. 3 to 6 actually includes with the flange portions 24 a and 24b.

As illustrated in FIGS. 3 to 6, the two annular members 10 each compriseradially outer projections 13 each formed by extending a radially outerside of one peripheral end portion of each of the pockets 12 in theaxial direction, radially inner recesses 14 each formed by recessing aradially inner side thereof, radially inner projections 15 each formedby extending a radially inner side of another peripheral end portion ofeach of the pockets 12 in the axial direction, and radially outerrecesses 16 each formed by recessing a radially outer side thereof.

In this way, in each of the two annular members 10, the one peripheralend portion of each of the pockets 12 has the radially outer projection13 and the radially inner recess 14, and the another peripheral endportion thereof has the radially inner projection 15 and the radiallyouter recess 16. Through employment of this structure, the annularmembers 10 of one type can be manufactured with the same die set andrespectively used as one of the annular members 10 and another of theannular members 10. Thus, manufacturing cost can be reduced.

In this structure, the radially outer projections 13 of the one of theannular members 10 are inserted into the radially outer recesses 16 ofthe another of the annular members 10, and the radially innerprojections 15 of the one of the annular members 10 are inserted intothe radially inner recesses 14 of the another of the annular members 10.With this, the radially outer projections 13 and the radially innerprojections 15 are engaged with each other in the axial direction.Further, engagement surfaces 13 a and 15 a of the radially outerprojections 13 and the radially inner projections 15 are inclined withrespect to the axial direction in a manner that the radially outerprojections 13 and the radially inner projections 15 are each thicker ona distal end side than on a proximal end side (refer to FIGS. 7 and 8).

As illustrated in FIGS. 3 and 5, the respective opposed surfaces 11 ofthe two annular members 10 are snap-fitted to each other, and theradially outer projections 13 and the radially inner projections areengaged with each other with a predetermined amount of interference inthe axial direction. As a result, a frictional force is generated alongeach of the engagement surfaces 13 a and 15 a of the radially outerprojections 13 and the radially inner projections 15. Further, theengagement surfaces 13 a and 15 a of the radially outer projections 13and the radially inner projections 15 are inclined with respect to theaxial direction in a manner that the radially outer projections 13 andthe radially inner projections 15 are each thicker on the distal endside than on the proximal end side. As a result, an axial component of areactive force generated in a normal direction of each of the engagementsurfaces 13 a and 15 a of the radially outer projections 13 and theradially inner projections 15 is provided.

The frictional force generated along each of the engagement surfaces 13a and 15 a of the radially outer projections 13 and the radially innerprojections 15, and the axial component of the reactive force generatedin the normal direction of each of the engagement surfaces 13 a and 15 aare applied synergistically with each other. Thus, even when asignificant centrifugal force is applied due to high rotation, the twoannular members 10 can be reliably prevented from being separated fromeach other in the axial direction.

In this way, at both the peripheral end portions of the pockets 12 ofthe annular members 10, the radially outer projections 13, the radiallyinner recesses 14, the radially inner projections 15, and the radiallyouter recesses 16 are provided as coupling portions 18. With this, inthe case where a significant centrifugal force is applied due to highrotation, even when the one of the annular members 10 and the another ofthe annular members 10 are to be separated from each other toward anouter side in the axial direction and the pockets 12 are to be opened,the balls 4 are easily kept received in the pockets 12 by the couplingportions 18 described above.

In the coupling structure of this embodiment, inclination angles θ(refer to FIGS. 7 and 8) of the engagement surfaces 13 a and 15 a of theradially outer projections 13 and the radially inner projections 15 eachneed to be set to 5° or more. When the inclination angles θ are set tothis value, deformation of the engagement surfaces 13 a and 15 a at thetime of application of a significant centrifugal force due to highrotation can be easily suppressed. As a result, the axial component ofthe reactive force can be reliably applied to the engagement surfaces 13a and 15 a, and hence a force of coupling the two annular members 10 toeach other can be easily secured. Note that, when the inclination anglesθ of the engagement surfaces 13 a and 15 a are each less than 5°, in thecase where a significant centrifugal force is applied due to highrotation, the deformation of the engagement surfaces 13 a and 15 a isdifficult to suppress. As a result, the axial component of the reactiveforce is difficult to reliably apply to the engagement surfaces 13 a and15 a.

Further, in this coupling structure, as illustrated in FIGS. 9 and 10,the radially inner projections 15 are formed to be thicker than theradially outer projections 13 (tIN>tOUT). When the radially innerprojections 15 are formed to be thicker than the radially outerprojections 13 in this way, at the time of the application of asignificant centrifugal force due to high rotation, the radially innerprojections 15 are deformed more significantly than the radially outerprojections 13. This is because the radially inner projections 15 arelarger than the radially outer projections 13 not only in thickness butalso in mass. Here, the engagement surfaces 13 a and 15 a of theradially outer projections 13 and the radially inner projections 15 areinclined with respect to the axial direction in a manner that theradially outer projections 13 and the radially inner projections 15 areeach thicker on the distal end side than on the proximal end side. Thus,the radially inner projections 15 are deformed to increase a force ofcoupling the engagement surfaces 13 a and 15 a of the radially outerprojections 13 and the radially inner projections 15 to each other.

By the way, the ball bearing 1 is used on the premise of oillubrication, and hence pocket clearances need to be secured so as toreduce shearing resistance of oil films. In the retainer 5 of thisembodiment, as illustrated in FIG. 6, a circumferential clearance m ofeach of the pockets 12 with respect to the balls 4 is set to be largerthan an axial clearance n thereof. In this way, when the circumferentialclearance m is set to be larger than the axial clearance n in each ofthe pockets 12, the following advantage can be obtained. In a case wherethe ball bearing 1 is used in an environment of a high moment load, evenwhen circumferential lead and lag of the ball 4 are to occur in each ofthe pockets 12 in accordance with an increase or a decrease in contactangle of the ball bearing 1, the lead and lag of the ball 4 can beabsorbed with the circumferential clearance m. As a result, an undesiredtensile load is not applied to the retainer 5, and hence durability ofthe retainer 5 can be enhanced.

In this case, in each of the pockets 12, it is effective to set thecircumferential clearance m to be 1.38 times or more as large as theaxial clearance n. With this setting, under a high moment load, thecircumferential lead and lag of the ball 4 in each of the pockets 12 canbe reliably absorbed with the circumferential clearance m. Note that, ineach of the pockets 12, when the circumferential clearance m is lessthan 1.38 times as large as the axial clearance n, the circumferentiallead and lag of the ball 4 in each of the pockets 12 are difficult toreliably absorb with the circumferential clearance m. Meanwhile, whenthe axial clearance n is set to be large, behavior of the balls 4becomes unstable, and hence such setting is inappropriate.

The two annular members 10 may be made of this kind of generally usedresin excellent in abrasion resistance, seizure resistance, and thelike, and examples thereof include synthetic resins such as apolyethylene, a polyamide, a polyacetal, a polyethylene terephthalate, apolybutylene terephthalate, a polycarbonate, a polyphenylene sulfide, apolyether sulfone, a polyether imide, a polyamide imide, a polyetherether ketone, a thermoplastic polyimide, a thermosetting polyimide, anepoxy resin, and a phenol resin. Further, it is possible to employ oneincluding a thermoplastic resin such as a polyamide, a polyphenylenesulphide, or a polyether ether ketone as a base material and glass fiberadded for strength improvement and dimensional stability.

However, in the present invention, a polyamide resin excellent intensile elongation, tensile strength, shock resistance, abrasionresistance, lubricity, and the like is preferred as the material for theretainer 5. Examples of the polyamide resin may include a polyamide 66(PA66), a polyamide 46 (PA46), a polyamide 9T (PA9T), a polyamide 11(PA11), and a polyamide 6 (PA6). As described above, according to thepresent invention, as a material for the retainer, there may be used apolyamide resin excellent in tensile elongation, tensile strength, shockresistance, abrasion resistance, lubricity, and the like. Accordingly,it is possible to provide a high-quality retainer. When an oil to beused contains a large amount of resin attacking components (phosphorousand sulfur), in terms of oil resistance superiority expressed byPPS>PA46>PA66, PPS is preferably used. Meanwhile, a relationship ofprices of the resin materials is expressed by PA66>PA46>PPS, and henceit is desired to select the material in consideration of the resinattacking property of the oil to be used. Note that, the outer race 3,the inner race 2, and the ball 4 are made of a metal such as bearingsteel and carburized steel.

Grease to be filled in the ball bearing is a semisolid lubricant formedof a base oil, a thickening agent, and an additive. The base oilconstituting the lubricating grease is not particularly limited as longas it is an oil generally used as base oil of lubricating grease, andexamples thereof include: mineral oils such as a paraffin-based mineraloil and a naphthene-based mineral oil; hydrocarbon-based synthetic oilssuch as a polybutene, a poly-α-olefin, an alkylbenzene, analkylnaphthalene, and an alicyclic compound; and a natural fat and oil,a polyol ester oil, a phosphate ester, a diester oil, a polyglycol oil,a silicone oil, a polyphenyl ether oil, an alkyldiphenyl ether oil, anda fluorinated oil as a nonhydrocarbon-based synthetic oil.

In addition, examples of the thickening agent include: metal soap-basedthickening agents such as aluminum soap, lithium soap, sodium soap,complex lithium soap, complex calcium soap, and complex aluminum soap;and urea-based compounds such as a diurea compound and a polyureacompound. Those thickening agents may be used alone, or two or morekinds thereof may be used in combination.

As a known additive for the lubricating grease, there are given, forexample: an extreme pressure agent; an antioxidant such as anamine-based or a phenol-based antioxidant; a metal deactivator such asbenzotriazole; a viscosity index improver such as a polymethacrylate ora polystyrene; and a solid lubricant such as molybdenum disulfide orgraphite. Those additives may be used alone, or two or more kindsthereof may be used in combination.

In the present invention, the ball non-contact surface 31 is provided inthe inner peripheral surface, and hence resistance generated at the timeof passage of a lubricant through the inside of the pockets can bereduced. Further, an amount of oil films to be formed between the balls4 and the pockets 12 can be reduced. With this, reduction in torque canbe achieved. In addition, the recess 32 forming the ball non-contactsurface 31 is opened in at least one of the pocket axial ends, and henceextra lubricant between the inner peripheral surface and the ball (steelball) can be discharged therethrough. As a result, the effect of theextra lubricant on the torque can be eliminated.

Further, the ball contact surface 30 is provided at a central portion ofthe inner peripheral surface, and hence the ball (steel ball) 4 can bestably retained in the pocket central portion. Thus, it is possible toprevent backlash of the ball 4, and provide a high-quality product. TheC-shape of the recess 32 forming the ball non-contact surface 31facilitates discharge of the lubricant between the inner peripheralsurface and the ball 4 due to a centrifugal force.

With the flange portions 24 a and 24 b provided as described above, itis possible to restrict inflow of the lubricant into the inside (insideof the bearing) and prevent outflow of the lubricant from the inside(inside of the bearing) to the outside of the bearing. Thus, effectivereduction in torque can be achieved. The end surfaces 21 on the oppositeside to the coupling portions of the annular members 10 are each formedinto the flat shape, and hence stirring resistance of the lubricant canbe reduced. As a result, further reduction in torque can be achieved.

Next, FIG. 11 illustrates a ball bearing using another retainer. In theretainer of this case, the ball contact surface 30 comprises an oblongportion 25 formed at a central portion in a pocket circumferentialdirection of the inner peripheral surface so as to reach both the pocketaxial ends. Further, the ball non-contact surface 31 comprises a pair ofcircular-arc recesses 26 and 26 provided on both sides in the pocketcircumferential direction of the ball contact surface 30. The recesses26 and 26 are each opened in both the pocket axial ends. In other words,the recesses 26 and 26 each extend from a retainer radially innersurface 10 b to reach the retainer radially outer surface 10 a, and areopened in each of the retainer radially inner surface 10 b and theretainer radially outer surface 10 a.

Note that, other structural details of the retainer 5 illustrated inFIG. 12 are the same as those of the retainer 5 illustrated in FIG. 2,and the ball bearing illustrated in FIG. 11 has the same structure asthat of the ball bearing illustrated in FIG. 1. Thus, the same parts(same members) of the retainer 5 illustrated in FIG. 12 and the ballbearing illustrated in FIG. 11 as those in FIGS. 1 and 2 are denoted bythe same reference symbols, and description thereof is omitted.

Also in this retainer 5, with the ball non-contact surface 31 providedas described above, it is possible to reduce the resistance generated atthe time of passage of a lubricant through the inside of the pockets,and an amount of oil films to be sheared due to movement of the balls.As a result, reduction in torque of the bearing (ball bearing) usingthis retainer can be achieved. Further, with the ball contact surface 30provided as described above, it is possible to prevent backlash of theball, and provide a high-quality product. Still further, in thisretainer, the extra lubricant between the inner peripheral surface andthe ball can be discharged from the bearing radially outer side and thebearing radially inner side. In this way, the surplus can removeinfluence on torque with the oil.

By the way, as illustrated in FIG. 13, the ball bearing normallycomprises seal portions 7 arranged in an annular space 6 formed betweenthe inner race 2 and the outer race 3. In this case, the outer race 3 ismounted to the fixed part such as the housing, and the inner race 2 ismounted to the rotary part such as the rotary shaft. The seal portions 7each comprise a seal member 8 b formed of an elastic member such asrubber bonded integrally with a metal core 8 a through vulcanization.The seal member 8 b comprises a proximal end portion mounted to aradially inner end portion of the outer race 3 on a fixed side, and adistal end portion provided with a seal lip 8 c held in contact with aradially outer end portion of the inner race 2. Note that, instead of aninner-race rotary type exemplified in this embodiment, the ball bearingis applicable also to an outer-race rotary type in which the inner race2 is mounted to the fixed part such as the housing and the outer race 3is mounted to the rotary part such as the rotary shaft.

As illustrated in FIG. 13, the ball bearing of the present invention issuited to a sealed ball bearing comprising the seal portions 7. Withthis, deformation of the retainer due to high-speed rotation can besuppressed, and reduction in torque can be achieved through therestriction on an amount of the inflow of a lubricant and the reductionof the stirring resistance. Thus, when this bearing is used in anautomobile, fuel efficiency becomes higher, and hence environmentallyfriendly driving can be performed. In other words, an automotive ballbearing suited to high rotation bearings used in electric vehicles andhybrid vehicles can be provided. In particular, this ball bearing isoptimum to automotive transmissions.

Hereinabove, description is made of the embodiments of the presentinvention. However, the present invention is not limited to theembodiments described above, and various modifications may be madethereto. As the shapes of the ball contact surface 30 and the ballnon-contact surface 31, various shapes other than those in the exampleof the figures can be employed as long as the ball contact surface 30 isarranged at least at the central portion of the inner peripheral surface(central portion in the pocket circumferential direction and centralportion in the pocket axial direction) and the ball non-contact surface31 is opened in any one of the pocket axial ends.

The ball non-contact surface 31 may be appropriately changed in size,depth, and the like in accordance, for example, with the lubricant to beused as long as both the resistance generated at the time of passage ofthe lubricant and the amount of oil films to be sheared can be reduced.

Further, in the bearing of FIG. 1, the ball non-contact surface 31 isopened to the outer race 3 side. However, in contrast, the ballnon-contact surface 31 may be opened to the inner race 2 side. Notethat, the number of the pockets for retaining the balls may bearbitrarily increased or reduced.

INDUSTRIAL APPLICABILITY

An automotive ball bearing suited to high rotation bearings used inelectric vehicles and hybrid vehicles can be provided.

REFERENCE SIGNS LIST

-   2 inner race-   3 outer race-   4 ball-   5 retainer-   6 annular space-   7 seal portion-   8 c seal lip-   10 annular member-   11 opposed surface-   12 pocket-   13 radially outer projection-   13 a engagement surface-   14 radially inner recess-   15 radially inner projection-   15 a engagement surface-   16 radially outer recess-   17 back surface-   21 end surface-   24 a flange portion-   24 b flange portion-   25 oblong portion-   26 recess-   30 ball contact surface-   31 ball non-contact surface-   32 recess-   θ inclination angle-   m circumferential clearance-   n axial clearance

The invention claimed is:
 1. A retainer for a ball bearing, comprisingtwo annular members that face each other in an axial direction thereof,the two annular members having opposed surfaces each comprisinghemispherical pockets that are formed at a plurality of positions in acircumferential direction of each of the two annular members andconfigured to receive balls, the opposed surfaces being snap-fitted toeach other so as to couple the two annular members to each other,wherein the hemispherical pockets each have an inner peripheral surfaceincluding a ball contact surface and a ball non-contact surface, whereinthe ball contact surface is formed at a central portion in a pocketcircumferential direction of the inner peripheral surface and at leastat a central portion in a pocket axial direction of the inner peripheralsurface, the pocket circumferential direction of the inner peripheralsurface being different from the circumferential direction of acorresponding one of the two annular members and the pocket axialdirection of the inner peripheral surface being different from the axialdirection of the two annular members, wherein the ball non-contactsurface comprises a recess that is recessed to an opposite side to acorresponding one of the balls across the ball contact surface, whereinthe recess is opened in at least one of pocket axial ends, wherein theball contact surface comprises an oblong portion formed at the centralportion in the pocket circumferential direction of the inner peripheralsurface so as to reach both the pocket axial ends, wherein the ballnon-contact surface comprises circular-arc recesses provided on bothsides of the ball contact surface in the pocket circumferentialdirection of the inner peripheral surface, and wherein the circular-arcrecesses are each opened in both the pocket axial ends.
 2. A retainerfor a ball bearing according to claim 1, further comprising couplingportions for coupling the two annular members to each other bysnap-fitting the opposed surfaces to each other, wherein the couplingportions are provided at both end portions in the pocket circumferentialdirection of the inner peripheral surface of each of the hemisphericalpockets, and wherein the two annular members each have a back surfacelocated on an opposite side to a corresponding one of the opposedsurfaces and formed into a flat shape over an entire periphery thereof.3. A retainer for a ball bearing according to claim 2, wherein thecoupling portions each comprise: a radially outer projection formed byextending, in the axial direction of the two annular members, a radiallyouter side of the end portion in the pocket circumferential direction ofthe inner peripheral surface of each of the hemispherical pockets of afirst of the two annular members so as to allow the inner peripheralsurface of each of the hemispherical pockets thereof to abut against thecorresponding one of the balls; a radially inner recess formed byrecessing a radially inner side of the end portion in the pocketcircumferential direction of the inner peripheral surface of each of thehemispherical pockets of the first of the two annular members; aradially inner projection formed by extending, in the axial direction ofthe two annular members, a radially inner side of the end portion in thepocket circumferential direction of the inner peripheral surface of eachof the hemispherical pockets of a second of the two annular members soas to allow the inner peripheral surface of each of the hemisphericalpockets thereof to abut against the corresponding one of the balls; anda radially outer recess formed by recessing a radially outer side of theend portion in the pocket circumferential direction of the innerperipheral surface of each of the hemispherical pockets of the second ofthe two annular members, wherein the radially outer projection and theradially inner projection are engaged with each other in the axialdirection of the two annular members by inserting the radially outerprojection into the radially outer recess and by inserting the radiallyinner projection into the radially inner recess, and wherein anengagement surface of the radially outer projection and an engagementsurface of the radially inner projection are inclined with respect tothe axial direction of the two annular members such that the radiallyouter projection and the radially inner projection are each thicker on adistal end side than on a proximal end side.